CNG Conversions Explained…

Commonly Misunderstood Facts about CNG Vehicles
CNG Conversions Explained…

Natural Gas Vehicles have been on the road for as long as gasoline vehicles have been around.
CNG (Compressed Natural Gas) Vehicles have been growing in popularity worldwide over the past 40 years. In the United States CNG Vehicles were brought into the forefront in 2008 due to the rocketing gasoline prices. Motorists faced with high gasoline prices started looking into CNG Vehicles as a natural alternative to gasoline vehicles with their lower fuel prices and cleaner emissions. In States that had existing CNG refueling infrastructure already in place the popularity of CNG vehicles and conversions just took off. Some of these states were Utah, California and Oklahoma.

One of the most misunderstood aspects of CNG Conversions is the “certification” process, whether it is CNG System Certification, CNG Technician Certification, CNG Component Certification or CNG Install Shop Certification. Throughout the world CNG System Components are tested and certified for safety. These ISO (International Organization for Standardization) standards insure that the compontents will function correctly and remain safe. Besides the ISO testing the CNG System Manufacturers usually train the technicians that will install their systems to insure correct tuning and safe installation.

Only in the United States has the notion of a CNG System being “certified” by a government agency been discussed. Like anything of interest that effects our wallets as the gas prices inched up in 2008 the discussion of CNG Conversions increased. Lots of information was discussed but unfortunately much of it was false and misinterpreted.

Before talking about what any certification may be able to do for us, lets talk about what the EPA (Environmental Protection Agency) has written concerning AFV (Alternative Fuel Vehicle) Conversions and “certification”.

In the beginning the EPA wanted Cleaner Air (The Clean Air Act)(1). They targeted some cities that did not meet their “standards”(2) and asked them to clean up their air. With the power of the Clean Air Act the EPA was now in a position to offer a solution. They then mandated that some“Covered Fleets”(3) should “convert” a certain percentage(4) of their vehicles to AFV (Alternative Fuel Vehicles) thus helping the air quality. They offered to “Certify” CNG conversions(5) through a process already in place which was being used by new vehicle manufacturers. This would be good for the Fleets, if their conversions were EPA approved this would make them eligible for Federal and State rebates(6) and Incentives.

What is an “EPA” certification? The EPA tests the CNG vehicle and uses DF’s (Deterioration Factors)(7) along with other tests to prove that the vehicle will continue to run clean throughout its useful life.(8) This “useful life” varies from 50,000 to 120,000 and up to 10 years(9) whichever comes first. The EPA only Certifies conversions for new vehicles. They do not certify older vehicles(10). That explains why “EPA” conversions are all newer vehicles. Finally a EPA Certification expires after the “useful life” of the vehicle. The EPA Certification of a CNG Conversion is a method whereby a company can test a CNG conversion and reliably assure their customers that the conversion will continue to run clean throughout the vehicles “useful life”. This Certification is similar to OEM (original equipment manufacturer) certification process that every car maker has to submit to. Similarly if a competent technician install a CNG conversion system on a vehicle and tunes it correctly, you will have the same outcome. Many CNG Conversion systems available today were “EPA Certified” for certain vehicles at some point but due to the cost and red tape these companies have chosen to not renew their certifications. A simple system whereby a state could check an installed CNG System for safety and emissions is all that is needed.

Now we can talk about what an EPA Certification can’t be or do. The statement that all CNG Conversions must be EPA Certified is false on it’s face. The EPA has never been able to Certify ALL Conversions. On top of that a “EPA Certified” conversion expires after the vehicles useful life. The EPA has never stated that ALL CNG Conversions must be approved. The only thing the EPA has said about ALL vehicles (CNG Conversions included) is concerning whether or not a person is “tampering”.(11)

The pertinent sections about tampering are below:

§ 7522. Prohibited acts

(3) (A) for any person to remove or render inoperative any device or element of design installed on or in a motor vehicle or motor vehicle engine in compliance with regulations under this sub chapter prior to its sale and delivery to the ultimate purchaser, or for any person knowingly to remove or render inoperative any such device or element of design after such sale and delivery to the ultimate purchaser; or
(B) for any person to manufacture or sell, or offer to sell, or install, any part or component intended for use with, or as part of, any motor vehicle or motor vehicle engine, where a principal effect of the part or component is to bypass, defeat, or render inoperative any device or element of design installed on or in a motor vehicle or motor vehicle engine in compliance with regulations under this sub-chapter, and where the person knows or should know that such part or component is being offered for sale or installed for such use or put to such use.

Are you confused yet? Let me define a few more of their terms, “ultimate purchaser” is the person who buys the new car. The “devices” mentioned are pollution devices like catalytic converters, engine monitoring devices, evaporative systems etc.. In (B) above they are talking selling a car part that defeats or renders inoperative the above mentioned devices.

The following actions are not tampering, Installing a CNG Conversion on a vehicle (it must be tuned correctly), taping into a wire for monitoring purposes such as RPM or TPS (throttle position sensor) and finally installing a Diesel/CNG system on a vehicle as long as the percentage of CNG is under 70% (if CNG is under 70% they are not classified as an AFV).

In layman’s terms the EPA just wants our vehicles to run clean….if we cause them to burn dirty we are “tampering”.

Modern CNG Conversion Systems do NOT defeat or render inoperative any Emission devices, a Sequential CNG system has its own monitoring devices, a coolant temp sensor, a MAP (manifold absolute pressure), a natural gas vapor temp and natural gas pressure sensor. If a CNG system is tuned correctly it will be fully compatible and compliant with all modern OBDII systems.

Now lets talk about CNG Certification of Shops, Technicians and System inspectors.

There are some Colleges that have AFV (Alternative Fuel Vehicle) training. ASE (automotive service excellence) has a Alternative Fuel Certification that is offered 2 times a year, it is the F1. CSA-America offers CNG Tank and System Inspection training..These are volinary trainings anyone can go to. The is no standard training for CNG Install Shops other than the CNG Component Manufacturers training.

The EPA is not a training institution, there is no State or Federal Mandated Certifications for Shops, Technicians or Inspectors. The most widely used safety standards for CNG conversions in the US are NFPA National Fire Protection Association 52 standards and they are self policing.

In Conclusion, EPA Certification is not required when someone does a conversion. Some installers choose certification in order to have assurance that a vehicle will continue to run clean “throughout its useful life”. As Mentioned above the “EPA certification” will expire after the useful life.
Everyone agrees that a CNG Conversion must be Safe and Clean. This can be accomplished through training (Utah has more trained CNG installers and inspectors than any other state), public awareness meetings and pride in our work. Last year there were more New CNG Conversions in Utah than the previous 5 years in the whole United States. It is time for Utah to pierce the veil of falsehoods spread about CNG Conversions. We need to step forward and take the lead by self governing of our own vehicles through State instituted CNG Safety and emission programs already in place.

In a year when unimployment is rising, everyone is fearful of the rising price of foreign oil and most people want a clean, low priced replacement for gasoline, to me CNG (a home grown fuel) is the only alternative….

10) (page 3 half way down: Retrofitting preMY2003 Vehicles)


About Jim: Jim Younkin is a mechanic with more than thirty years experience in automotive repair. His passions include car racing, mountain climbing, ice climbing, and CNG conversions. He enjoys sharing his passions and connecting with other of like mind. See more about Jim at
email: or 801-427-2284

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